Rotordynamic systems, such as turbomachinery (e.g., gas and steam turbines, compressors), generators, and other rotating machinery (e.g., electric motor driven systems) are generally monitored, continuously or intermittently, to, for example, control operation, protect against failure (which can be catastrophic and/or hazardous), assess fatigue, diagnose problems, and/or determine whether maintenance is required. Typically, turbomachinery includes radial (lateral) vibration and axial (longitudinal) displacement monitoring equipment, which is configured for long-term continuous and/or intermittent monitoring, without requiring the turbomachinery to be shutdown.
However, turbomachinery is usually not outfitted with angular or torsional oscillation monitoring equipment. Moreover, most known techniques for torsional vibration monitoring of rotordynamic systems are not well-suited for continuous (or intermittent) monitoring, and typically require shutting down the system to install the torsional vibration monitoring equipment (and to remove the equipment after testing. Additionally, such systems are intrusive and not certified for working in a potentially explosive, classified area which may include, for example, a purge system and, in some cases, a cooling system if the measurement has to be carried out in a hot area (e.g., next to a gas turbine exhaust duct). In the oil and gas business, system shutdown is often associated with a large monetary cost due to, for example, losses in oil and gas production and/or losses in energy generation.
Additionally, in the oil and gas industry, increasingly complex applications and tailor-made designs for individual customers present new and more complex rotor dynamic challenges. As a consequence, in addition to lateral vibration and/or axial displacement monitoring, torsional vibrations should be monitored and investigated during testing (e.g., to validate design) as well as during operation on-site over the long-term (e.g., continuously or intermittently, such as periodically, or in an on-demand or as-needed basis when unexpected issues occur). In other words, further advances in rotordynamic systems should provide built-in or in situ torsional vibration monitoring, which may operate continuously or intermittently, or as otherwise needed, and may be invoked while the turbomachinery is on-line, without requiring system shutdown. Accordingly, it would be desirable to design methods and systems for angular and torsional vibration measurement for turbomachinery.